The other day I was sawing through a piece of wood on the woodpile and as I finished the cut, the blade hit a log below it and snapped back towards my face. It sent a chill of adrenaline that I felt somehow in my ears. Very scary.
This time the blade didn't reach my face, but if it had, the mask would've stopped it from carving up flesh.
I urge you chain saw users: get one of these. $50 or so. Play it safe, please. The more hours you've operated chainsaws, the more the chance of a freak accident. Experience doesn't make you invulnerable.
PS I always sharpen the teeth after use, so it's ready when I next pick it up.